1. Field of the Invention
This invention relates to an apparatus for recording digital video data. In addition, this invention relates to an apparatus for reproducing digital video data. Also, this invention relates to an apparatus for recording and reproducing digital video data.
2. Description of the Related Art
In general, traffic-condition monitoring systems, automatic-cash dispenser monitoring systems, and other monitoring systems include television cameras for converting scenes of interest into corresponding video signals. The video signals generated by the television cameras are recorded on suitable recording mediums such as magnetic tapes, magnetic discs, or magneto-optical discs.
In some monitoring systems, recording mediums are required to continuously record a video signal for 24 hours. Usual magnetic discs and magneto-optical discs have relatively-small recording capacities so that they are unsuited to such long-time continuously recording of video signals.
Japanese published unexamined patent application 8-237600 discloses a monitoring system in which an original video signal is deteriorated into a lower-data-rate video signal, and a hard disc drive (HDD) records the lower-data-rate video signal on a magnetic disc. The deterioration of the original video signal into the lower-data-rate video signal enables a longer recording time.
There are time-lapse VTR""s (video tape recorders) which intermittently execute recording for 24 hours. It is known to use such a time-lapse VTR in recording a video signal generated by a monitoring system. In the time-lapse VTR, a search for a desired scene represented by the video signal on a magnetic tape tends to take a relatively long access time.
It is a first object of this invention to provide an improved apparatus for recording digital video data.
It is a second object of this invention to provide an improved apparatus for reproducing digital video data.
It is a third object of this invention to provide an improved apparatus for recording and reproducing digital video data.
A first aspect of this invention provides a digital data recording and reproducing apparatus comprising a first recording medium having a first recording capacity; a second recording medium having a second recording capacity greater than the first recording capacity; first means for recording an input digital video signal on the first recording medium as an inward-flow signal; second means for transferring the inward-flow signal from the first recording medium to the second recording medium each time an amount of the inward-flow signal on the first recording medium reaches a first predetermined amount; third means for transferring the digital video signal from the second recording medium to the first recording medium as an outward-flow signal; fourth means for reading out the outward-flow signal from the first recording medium as an output digital video signal; fifth means for, during a search, reading out the outward-flow signal from the first recording medium; sixth means for, during the search, monitoring an amount of the outward-flow signal on the first recording medium which has not yet been read out by the fifth means; and seventh means for, during the search, transferring the digital video signal from the second recording medium to the first recording medium when the amount monitored by the sixth means decreases to a second predetermined amount.
A second aspect of this invention provides a digital data reproducing apparatus comprising a first recording medium having a first recording capacity and storing a digital video signal; a second recording medium having a second recording capacity smaller than the first recording capacity; first means for transferring the digital video signal from the first recording medium to the second recording medium; second means for reading out the digital video signal from the second recording medium as an output digital video signal; third means for, during a search, reading out the digital video signal from the second recording medium; fourth means for, during the search, monitoring an amount of the digital video signal on the second recording medium which has not yet been read out by the third means; and fifth means for, during the search, transferring the digital video signal from the first recording medium to the second recording medium when the amount monitored by the fourth means decreases to a second predetermined amount.
A third aspect of this invention is based on the second aspect thereof, and provides a digital data reproducing apparatus wherein the fifth means comprises means for writing the digital video signal on the second recording medium on an overwrite basis.
A fourth aspect of this invention is based on the second aspect thereof, and provides a digital data reproducing apparatus wherein the second predetermined amount corresponds to about one third of a given recording area of the second recording medium.
A fifth aspect of this invention provides a digital data recording apparatus comprising a first recording medium having a first recording capacity; a second recording medium having a second recording capacity greater than the first recording capacity; first means for recording a digital video signal on the first recording medium; second means for detecting an amount of the digital video signal on the first recording medium; and third means for transferring the digital video signal from the first recording medium to the second recording medium each time the amount detected by the second means reaches a predetermined amount; wherein the recording of the digital signal on the first recording medium by the first means and the transfer of the digital video signal from the first recording medium by the third means are implemented on a time sharing basis.
A sixth aspect of this invention is based on the fifth aspect thereof, and provides a digital data recording apparatus further comprising a signal compressor for compressing an input video signal into a compression-resultant video signal, and for outputting the compression-resultant video signal to the first means as the digital video signal.
A seventh aspect of this invention is based on the sixth aspect thereof, and provides a digital data recording apparatus wherein a data rate related to the transfer of the digital video signal to the second recording medium by the third means is greater than a data rate related to the digital video signal outputted by the signal compressor.
An eighth aspect of this invention is based on the fifth aspect thereof, and provides a digital data recording apparatus wherein the second recording medium comprises a magnetic tape.
A ninth aspect of this invention provides a digital data recording and reproducing apparatus comprising a first recording medium having a first recording capacity; a second recording medium having a second recording capacity greater than the first recording capacity; first means for recording an input digital video signal on the first recording medium as an inward-flow signal; second means for transferring the inward-flow signal from the first recording medium to the second recording medium each time an amount of the inward-flow signal on the first recording medium reaches a predetermined amount; third means for transferring the digital video signal from the second recording medium to the first recording medium as an outward-flow signal; and fourth means for reading out the outward-flow signal from the first recording medium as an output digital video signal.
A tenth aspect of this invention is based on the ninth aspect thereof, and provides a digital data recording and reproducing apparatus wherein a data rate related to the transfer of the digital video signal to the second recording medium by the second means is greater than a data rate related to the input digital video signal.
An eleventh aspect of this invention is based on the ninth aspect thereof, and provides a digital data recording and reproducing apparatus further comprising fifth means for collating a portion of the digital video signal on the second recording medium with a corresponding portion of the inward-flow signal on the first recording medium to decide whether or not the portion of the digital video signal on the second recording medium is correct.
A twelfth aspect of this invention is based on the eleventh aspect thereof, and provides a digital data recording and reproducing apparatus further comprising sixth means for transferring the portion of the inward-flow signal from the first recording medium to the second recording medium when the fifth means decides that the portion of the digital video signal on the second recording medium is not correct.
A thirteenth aspect of this invention is based on the ninth aspect thereof, and provides a digital data recording and reproducing apparatus further comprising fifth means for deciding whether or not the amount of the inward-flow signal on the first recording medium reaches a given amount, and sixth means for generating a warning signal when the fifth means decides that the amount of the inward-flow signal on the first recording medium reaches the given amount.
A fourteenth aspect of this invention provides a digital data reproducing apparatus comprising a first recording medium having a first recording capacity and storing a digital video signal; a second recording medium having a second recording capacity smaller than the first recording capacity; first means for transferring the digital video signal from the first recording medium to the second recording medium; and second means for reading out the digital video signal from the second recording medium as an output digital video signal.
A fifteenth aspect of this invention provides a digital data recording apparatus comprising a first recording medium having a first recording capacity; a second recording medium having a second recording capacity greater than the first recording capacity; first means for recording a digital video signal on the first recording medium; second means for detecting an amount of the digital video signal on the first recording medium; third means for transferring the digital video signal from the first recording medium to the second recording medium each time the amount detected by the second means reaches a predetermined amount; fourth means for extracting portions of the digital video signal and combining the extracted portions into a digest signal; fifth means for recording the digest signal generated by the fourth means on the first recording medium; and sixth means for transferring the digest signal from the first recording medium to the second recording medium.
A sixteenth aspect of this invention is based on the fifteenth aspect thereof, and provides a digital data recording apparatus wherein the fourth means comprises means for periodically extracting portions of the digital video signal at a predetermined period and combining the extracted portions into the digest signal.
A seventeenth aspect of this invention is based on the fifteenth aspect thereof, and provides a digital data recording apparatus wherein each of the portions of the digital video signal which are extracted by the fourth means corresponds to a given number of successive frames.
An eighteenth aspect of this invention is based on the fifteenth aspect thereof, and provides a digital data recording apparatus further comprising seventh means for deciding whether or not the second recording medium is requested to be ejected, and eighth means for, in cases where the seventh means decides that the second recording medium is requested to be ejected, allowing the second recording medium to be ejected after the sixth means transfers the digest signal from the first recording medium to the second recording medium.
A nineteenth aspect of this invention is based on the fifteenth aspect thereof, and provides a digital data recording apparatus wherein the second recording medium has a first region assigned to the digital video signal and a second region assigned to the digest signal, the second region preceding the first region as viewed along a normal playback direction.
A twentieth aspect of this invention is based on the fifteenth aspect thereof, and provides a digital data recording apparatus further comprising seventh means for recording a position marking signal on the second recording medium, the position marking signal representing positions of portions of the digital video signal on the second recording medium which correspond to the digest signal.
A twenty-first aspect of this invention provides a digital data recording and reproducing apparatus comprising a first recording medium having a first recording capacity; a second recording medium having a second recording capacity greater than the first recording capacity; first means for recording an input digital video signal on the first recording medium as an inward-flow video signal; second means for transferring the inward-flow video signal from the first recording medium to the second recording medium each time an amount of the inward-flow video signal on the first recording medium reaches a first predetermined amount; third means for transferring the digital video signal from the second recording medium to the first recording medium as an outward-flow video signal; fourth means for reading out the outward-flow video signal from the first recording medium as an output digital video signal; fifth means for extracting portions of the input digital video signal and combining the extracted portions into an inward-flow digest signal; sixth means for recording the inward-flow digest signal generated by the fifth means on the first recording medium; seventh means for transferring the inward-flow digest signal from the first recording medium to the second recording medium; eighth means for transferring the digest signal from the second recording medium to the first recording medium as an outward-flow digest signal; and ninth means for reading out the outward-flow digest signal from the first recording medium as an output digest signal.
A twenty-second aspect of this invention is based on the twenty-first aspect thereof, and provides a digital data recording and reproducing apparatus further comprising tenth means for deciding whether or not the second recording medium is newly placed in position, and eleventh means for, in cases where the tenth means decides that the second recording medium is newly placed in position, allowing the eighth means to transfer the digest signal from the second recording medium to the first recording medium.
A twenty-third aspect of this invention is based on the twenty-first aspect thereof, and provides a digital data recording and reproducing apparatus further comprising tenth means for recording a position marking signal on the second recording medium, the position marking signal representing positions of portions of the digital video signal on the second recording medium which correspond to the digest signal.
A twenty-fourth aspect of this invention is based on the twenty-third aspect thereof, and provides a digital data recording and reproducing apparatus further comprising eleventh means for deciding whether or not reproduction of the digital video signal is requested; twelfth means for, when the eleventh means decides that the reproduction of the digital video signal is requested, referring to the marking signal and allowing the third means to transfer the digital video signal from the second recording medium to the first recording medium in response to the marking signal; and thirteenth means for, when the eleventh means decides that the reproduction of the digital video signal is requested, allowing the fourth means to read out the outward-flow video signal from the first recording medium.
A twenty-fifth aspect of this invention is based on the twenty-fourth aspect thereof, and provides a digital data recording and reproducing apparatus wherein each of the portions of the digital video signal which are extracted by the fifth means corresponds to a given number of successive frames, and the twelfth means comprises means for starting the third means transferring the digital video signal from a portion temporally preceding a requested portion.
A twenty-sixth aspect of this invention is based on the twenty-fourth aspect thereof, and provides a digital data recording and reproducing apparatus wherein each of the portions of the digital video signal which are extracted by the fifth means corresponds to a given number of successive frames.
A twenty-seventh aspect of this invention is based on the twenty-sixth aspect thereof, and provides a digital data recording and reproducing apparatus wherein the input digital video signal represents a sequence of different programs, and the portions of the digital video signal which are extracted by the fifth means correspond to starting portions of the programs respectively.
A twenty-eighth aspect of this invention is based on the twenty-first aspect thereof, and provides a digital data recording and reproducing apparatus wherein the fourth means comprises means for periodically extracting first portions of the digital video signal at a predetermined period and arranging the extracted first portions into a first component of the digest signal, and means for extracting second portions of the digital video signal and arranging the extracted second portions into a second component of the digest signal, and wherein each of the second portions of the digital video signal corresponds to a given number of successive frames.
A twenty-ninth aspect of this invention is based on the twenty-eighth aspect thereof, and provides a digital data recording and reproducing apparatus further comprising tenth means for deciding whether or not reproduction of the digital video signal is requested; eleventh means for, when the tenth means decides that the reproduction of the digital video signal is requested, referring to the marking signal corresponding to the first portions of the digital video signal and allowing the third means to transfer the second portions of the digital video signal from the second recording medium to the first recording medium in response to the marking signal; thirteenth means for, when the tenth means decides that the reproduction of the digital video signal is requested, allowing the fourth means to read out the second portions of the digital video signal from the first recording medium; fourteenth means for, when the tenth means decides that the reproduction of the digital video signal is requested, allowing the third means to transfer the digital video signal from the second recording medium to the first recording medium after the third means transfers the second portions of the digital video signal from the second recording medium to the first recording medium; and fifteenth means for, when the tenth means decides that the reproduction of the digital video signal is requested, allowing the fourth means to read out the outward-flow video signal from the first recording medium after the fourth means reads out the second portions of the digital video signal from the first recording medium.